docs: def render(self, **kwargs):
          """Renders the HTML representation of the element."""
          self.color_domain = [self.vmin + (self.vmax-self.vmin) * k/499. for
                               k in range(500)]
          self.color_range = [self.__call__(x) for x in self.color_domain]
          self.tick_labels = legend_scaler(self.index)
  
          super(ColorMap, self).render(**kwargs)
  
          figure = self.get_root()
          assert isinstance(figure, Figure), ('You cannot render this Element '
                                              'if it is not in a Figure.')
  
          figure.header.add_child(JavascriptLink("https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"), name='d3')